This invention relates to the extension or retraction of telescopic supports that are used to secure the mirror head of a rear vision mirror to a mounting bracket on a motor vehicle.
Although one application is with a rear vision mirror assembly, it should be realised that the invention should not be restricted to this particular application, as it will be suited to other applications. However, for ease of description, the invention will be described in relation to this application.
It is desirable to be able to move the mirror head, which holds the mirror, with respect to the mounting bracket on the motor vehicle in towards or away from the mounting bracket.
This enables the mirror head to be either positioned close to the side of the motor vehicle, or to be extended away from the motor vehicle to provide an increased field of view. A rear view may be obstructed by a vehicle body, a load on the vehicle, or a trailer that is being towed. In many of these instances, extending the mirror head outwardly will provide a increased field of view behind the vehicle.
Accordingly, it is an aim of the invention to provide a mechanism to extend or retract telescopic supports.
It is a further object of this invention to provide a means whereby a mirror head can be both manually or automatically moved towards or away from the mounting bracket of a motor vehicle mirror.
According to one aspect, the invention is a retraction and extension mechanism for extending or retracting a set of telescopic supports that connect a mirror head to a mirror mounting bracket comprising:
a mirror mounting bracket,
a mirror head,
a first tube projecting from said mounting bracket,
a support projecting from said mirror head that locates into and slides back and forth within said first tube,
a roller mounted with respect to said support,
a cable, attached at one end with respect to said first tube at a point between said roller and said mirror head, and extending to and around said roller and into said mirror head, the other end of said cable extending into and attached with respect to said first tube,
a capstan within said mirror head engaging said cable, and
a motor to drive said capstan in either direction to cause said mirror head to extend or retract with respect to said mirror mounting bracket.
The support may also comprise a tube and more than one set of telescopic first and second tubes may be used to mount the mirror head to the mirror bracket.
Preferably, a pair of first and second tubes are used, with one set of first and second tubes being located above the other set. A first cable extends from a connector in the upper tube set into the mirror head, around the capstan and into the lower set of first and tubular arms, around a roller in the end of the second tube in the lower set and back to a connector. A second cable extends from the other side of the lower connector into the mirror head, around at least one idler pulley and then into the upper set of first and second tubes. The end of this second cable is attached to the connector in the upper set via a roller that is mounted in the end of the second tube of the upper set. Movement of the first cable by the capstan will result in movement of the mirror head either towards or away from the mounting bracket. This will be described in more detail below in respect of a preferred embodiment.
Further, the invention may comprise a drive means for a cord comprising: a pair of contra rotating capstans that are rotatably mounted to a motor housing, said cable engaging with said capstans so that, with respect to each direction of movement of said cable through said drive means, the cable moves around the axis of one capstan in a direction opposite to that of the other capstan,
a pivot that allows said motor housing to rotate about an axis which is parallel to the axis of rotation of each of the capstans so that the extent of contact between the cable and the periphery of each capstan can be varied, and
torsion means acting with respect to said motor housing and pivot that acts to rotate said motor housing and to increase the extent of contact of said cable with respect to the periphery of each said capstan.
Preferably, the pivot is located equally distant between the axis of rotation of each capstan. This ensures that the extent of rotation of the axis of each capstan around the pivot is the same.
The torsion means may comprise either a torsion spring concentric with the pivot, or a coil spring fixed at one end with respect to the mirror head and attached to the motor housing at the other. The torsion means acts to rotate the motor housing in a direction which increases the extent of cable which is in contact with the periphery of each of the capstans. The torsion means is required to maintain at least a minimum degree of contact to ensure adequate drive connection between each of the capstans and the cable. If the extent of contact between the cable and the capstans becomes less than the minimum, then the cable will slip with respect to each of the capstans.
In one aspect of the invention, this is quite useful. If movement of the cable is prevented for whatever reason, then continued rotation of the capstans will tend to rotate the motor housing so that the extent of engagement between the cable and each of the capstans is reduced. This rotation, against the torsion means, will continue until the capstans start slipping with respect to the cable. At this point, the motor housing will cease rotating while maintaining sufficient force to act against the torsion means, and to thereby prevent any overload or stalling of the capstans. It will also be useful if the mirror head is moved manually. This will also cause rotation of the motor housing and result in slipping of the cable.
Preferably, one of the capstans is driven by an electric motor via reduction gearing, and the other capstan is driven via engaging ring gears that are on each of the capstans. This results in the contra rotation of the capstans.
The cable used on both the means for moving the mirror head and the drive means may comprise in a cord, belt or any other form of flexible cord. In addition, multiple cables may be used to produce a series of parallel cables that, together, act as a single cable.
As an alternative to contra rotating capstans, a single driven capstan may be used. The capstan may be spring loaded, or arranged in some other manner, so that it is pushed into the cable. The resultant angle of wrap must be sufficient to enable drive force to be applied to the cable. Any resistance to movement or any manual movement of the mirror head will result in deflection of the spring and slippage of the cable over the capstan.
A further alternative for the drive means may be a capstan in combination with a clutch. The clutch is designed to disengage upon manual movement or any resistance to movement being encountered.
In a second aspect, the invention is a retraction and extension mechanism for extending or retracting telescopic supports that connects a mirror head to a mirror mounting bracket comprising:
at least one first tube attached at one end to, and projecting from, said mirror mounting bracket,
at least one support attached to and projecting from said mirror head, that locate into and slide back and forth within a said first tube,
at least one wheel secured with respect to said support, the periphery of said wheel engaging against said first tube, and
drive means for rotating said wheel in either direction to move said first tube and support with respect to each other to cause said mirror head to extend or retract with respect to said mirror mounting bracket.
Preferably, the support comprises a tube and a pair of first and second tubes are used with one set of first and second tubes being located above the other set. The wheel and associated drive means may be located in one of the sets, or alternatively a wheel with associated drive means may be located in each of the sets of first and second tubes.
Preferably, the mounting of the wheel within one of the tubes includes a means of forcing the periphery of the wheel against one of the tubes. This may include a mounting which enables the wheel to move in a direction that is normal with respect to its axis of rotation and a spring means which pushes the wheel in the required direction.
Preferably, the wheel is mounted with respect to the tube which is located internally of the other tube. An aperture may be provided within the internal tube to enable the periphery of the wheel to locate against the outer tube.
In addition to the use of one wheel, two or more wheels may be used to provide the necessary drive force.
In addition to providing drive force, another function performed by the wheels will be to hold the mirror head in the required position while at the same time allowing manual movement of the mirror head without operation of the drive means. The friction force acting between the periphery of the wheel and one of the tubes must be sufficient to enable the wheel to move the mirror head. In addition, when the wheel is stationary, the applied force and resultant friction is high enough to prevent unwanted movement of the mirror head. The necessary force that will achieve these aims is not so large that it prevents manual movement of the mirror head. Manual movement will result in slippage of the wheel with respect to one of the tubes. Accordingly, with this invention, it is possible to manually move the mirror head to an extended or retracted position.
The wheel or wheels may be electrically driven, and the drive means preferably comprises an electric motor and drive pulley that is located within the mirror head and a cable which extends from the pulley into the telescopic tubes and that engages the wheel so as to cause it to rotate.
The cable within the telescopic tubes may either locate around the periphery of the wheel or some other element of the wheel which causes it to rotate. Alternatively, a pair of spaced wheels may have the cable located around them with an idler pulley, positioned between the pair of wheels, that pushes against the cable and in turn causes the cable to push against the pair of wheels. The pair of wheels may be slidably mounted with respect to their pivot to enable movement normal to the axis of the pivot to thereby cause the periphery of the wheels to bear against the inside surface of one of the tubes.
In order to fully understand the invention, a preferred embodiment will now be described, however it should be realised that the scope of this invention is not to be confined or restricted to the precise features of the embodiment.